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Patagonia Yields One of the Latest Megaraptorids: Joaquinraptor Casali Described Near the K–Pg Boundary

The unusually complete skeleton with a crocodiliform bone in its jaws clarifies their anatomy, illuminating their evolutionary position.

Overview

  • The new genus and species, Joaquinraptor casali, is described from the Lago Colhué Huapi Formation in Chubut and is among the geologically youngest megaraptorids, according to a study in Nature Communications.
  • The specimen preserves a partial skull, vertebrae, ribs, and both fore and hind limb elements, ranking it among the most complete members of the group.
  • A crocodiliform humerus found between the jaws suggests feeding behavior involving crocodyliforms, though the authors caution the evidence is not conclusive.
  • Histology records at least 19 growth lines, and researchers estimate the animal exceeded seven meters in length and weighed roughly a tonne.
  • Phylogenetic analyses in the paper indicate megaraptorans may nest closer to coelurosaurians—potentially as relatives of tyrannosaurids—reshaping views of late Gondwanan predator evolution.